You must be on the main phone on jack 01 to set time.  You can determine if your phone is jack 01 by setting the switch on the end of a display phone to PROGRAM and then pushing the number 6 on the dial pad.  The phone will read the jack and extension number.  When you have determined the jack 01 phone, do the following.

1. Set switch on end of phone to "PROGRAM" (or push PROGRAM key if you have one)
2. Dial "0"
3. Enter year (last 2 digits)
4. Enter month (01-12)
5. Enter day (01-31)
6. Enter day of week (Sun 0, Mon 1, Tue 2, Wed 3, Thu 4, Fri 5, Sat 6.)
7. Enter Hour (01-12)
8. Enter Minute (00-59)
9. Press 0 for AM 1 for PM
10. Press "AUTO DIAL/STORE" key
11. Return phone switch to "SET" (or push PROGRAM key if you have one)